Powershell: unexpected behavior of negated -like and -match conditionals - regex

Question

I have 2 folders in my windows folder, software, and softwaretest.
So I have the main folder "software" if statement, then jump to the elseif - here I have the backup folder, so jump to the else...
my problem is that I'm getting the write-host from the elseif, and I have a backup folder that I'm calling softwaretest, so can't see why it give me that output and not the else.
hope someone can guide/help me :-)
If ($SoftwarePathBackup = Get-ChildItem -Path "$Env:SystemRoot" | Where-Object { (!$_.Name -like 'software') }) {
Write-Host ( 'There are no folder named \software\ on this machine - You cant clean/clear/empty the folder!' ) -ForegroundColor Red;
} elseif ($SoftwarePathBackup = Get-ChildItem -Path "$Env:SystemRoot" | Where-Object { ($_.Name -match '.+software$|^software.+') } | Sort-Object) {
Write-Host ( 'There are none folder-backups of \software\ on this machine - You need to make a folder-backup of \software\ before you can clean/clear/empty the folder!' ) -ForegroundColor Red;
} else {
Remove-Item
}

Answer 1

I find it very confusing, to have the negation on the right or even in the RegEx. I think it would be more obvious, to negate in the beginning with a ! or -not.
To test, if a folder exist, you can use Test-Path. Test-Path also has a -Filter parameter, which you can use instead of Where-Object. But I think you don't even have to filter.
$SoftwarePath = "$($Env:SystemRoot)\Software", "$($Env:SystemRoot)\SoftwareBackup"
foreach ($Path in $SoftwarePath) {
if (Test-Path -Path $Path) {
Remove-Item -Path $Path -Force -Verbose
}
else {
Write-Output "$Path not found."
}
}
Would that work for you?

Answer 2

Your primary problem is one of operator precedence:
!$_.Name -like 'software' should be ! ($_.Name -like 'software') or, preferably,
$_.Name -notlike 'software' - using PowerShell's not-prefixed operators for negation.
Similarly, you probably meant to negate $_.Name -match '.+software$|^software.+' which is most easily achieved with $_.Name -notmatch '.+software$|^software.+'
As stated in Get-Help about_Operator_Precedence, ! (a.k.a. -not) has higher precedence than -like, so !$_.Name -like 'software' is evaluated as (!$_.Name) -like 'software', which means that the result of !$_.Name - a Boolean - is (string-)compared to wildcard pattern 'software', which always returns $False, so the If branch is never entered.
That said, you can make do without -like and -match altogether and use the implicit wildcard matching supported by Get-Item's -Include parameter (snippet requires PSv3+):
# Get folders whose name either starts with or ends with 'software', including
# just 'software' itself.
$folders = Get-Item -Path $env:SystemRoot\* -Include 'software*', '*software' |
Where-Object PSIsContainer
# See if a folder named exactly 'software' is among the matches.
$haveOriginal = $folders.Name -contains 'software'
# See if there are backup folders among the matches (too).
# Note that [int] $haveOriginal evaluates to 1 if $haveOriginal is $True,
# and to 0 otherwise.
$haveBackups = ($folders.Count - [int] $haveOriginal) -gt 0
# Now act on $folders as desired, based on flags $haveOriginal and $haveBackups.
Note how Get-Item -Path $env:SystemRoot\* is used to explicitly preselect all items (add -Force if hidden items should be included too), which are then filtered down via -Include.
Since Get-Item - unlike Get-ChildItem- doesn't support -Directory, | Where-Object PSIsContainer is used to further limit the matches to directories (folders).
Note: Get-ChildItem was not used, because -Include only takes effect on child (descendant) items (too) when -Recurse is also specified; while -Recurse can be combined with -Depth 0 (PSv3+) in order to limit matching to immediate child directories, Get-ChildItem apparently still tries to read the entries of all child directories as well, which can result in unwanted access-denied errors from directories that aren't even of interest.
In other words: Get-ChildItem -Recurse -Depth 0 -Directory $env:SystemRoot -include 'software*', '*software' is only equivalent if you have (at least) read access to all child directories of $env:SystemRoot.